Cancer and uncontrolled cell division #
- In cancer: genes that control cell division mutate, cells divide over and over again, forming an irregular mass of cells.
- In malignant tumour: some of cancer cells may break off and start to form new tumours elsewhere in the body.
- Several genes must mutate before a cell becomes cancerous.
- The risk is increased by factors that cause mutation (carcinogenic factors):
- ionising radiation (from X ray and radioactive sources emitting α, β or γ radiation)
- ultraviolet radiation (in sunlight)
- chemicals (e.g. asbestos, some component in tar from tobacco smoke)
- viruses (e.g. human papilloma virus – HPV, causing cervical cancer)
The stages involved in the development of cancer #
- oncogenes transformed by carcinogens
- cancerous cell does not respond to signal from other cells.
- mitosis
- cancerous cells not removed by immune system
- rapid mitosis
- tumor gets bigger. Cells change their characteristics and can be detected under the microscope.
- Tumor supplied with blood and lymph vessels. Tumor cells spread in blood and lymph to other parts of the body
- metastasis- cell invade other tissues. Secondary cancers form throughout the body
